The present invention is directed to transfer type heat sensitive recording medium adapted to be employed in a transfer type heat sensitive recording device and more specifically to a transfer type heat sensitive recording medium of the type having a base layer, an ink layer, and a coating layer which can be dissolved into the ink layer when heated to a specific temperature.
In a transfer type heat sensitive recording device, thermal pulses are applied to a transfer type heat sensitive recording medium so that ink is selectively transferred onto a recording sheet to record picture data.
FIG. 1 shows a conventional method of applying thermal pulses to such a heat sensitive recording medium. The recording medium 10 is prepared by forming an ink layer 12, 4 to 10 .mu.m in thickness on one surface of a base sheet 11 about 10 to 20 .mu.m in thickness. The base sheet 11 is, for instance, of condenser paper. The ink layer 12 is made of a material which is fluidized or sublimated by heating. The base sheet 11 is brought in contact with a thermal head 21 and thermal pulses are applied to the heat sensitive recording medium 10 when the sheet 11 comes to desired positions. A thermal pulse advances in the base sheet 11 radially as indicated by the arrows to the ink layer 12 to heat a part 13A of the latter. As a result, the part 12A of the ink layer 12 which has been fluidized or sublimated by heating is transferred onto a recording sheet (or an ordinary sheet) which is placed on the ink layer 12.
In the conventional transfer type heat-sensitive recording medium, the part 12A of the ink layer which is transferred by diffusion of heat in the base sheet is considerably wide. That is, the width l.sub.1 of the part 12A is much larger than the application width l.sub.0 of the thermal pulse from a heat supplying source such as the thermal head 21. Accordingly, the resolution is limited.
FIG. 2 is a graphical representation indicating the thicknesses of base sheets with the corresponding upper limits of resolution when the base sheets are of condenser paper. If the base sheet is relative thick, then the resultant resolution is not sufficient. Accordingly, when a recording is to be made with high resolution, it is essential to use a thin base sheet. However, employment of a thin base sheet suffers from the drawback that the heat-sensitive recording medium becomes wrinkled or wavy while being conveyed.